PbE (E = S, Se) Colloidal Quantum Dot-Layered 2D Material Hybrid Photodetectors

The size-dependent valence and conduction band-edge energies of Cu quantum dots

Ultra-small metal particles having band gaps are regarded as a new class of functional materials. We investigated the size dependencies of the band-edge energies on Cu quantum-dots in the size range of 0.7-2.1 nm. The extremely high conduction band-edge energies owing to the strong quantum-size effects were observed for sizes below 1 nm.

Room Temperature Broadband Bi2Te3/PbS Colloidal Quantum Dots Infrared Photodetectors

Lead sulfide colloidal quantum dots (PbS CQDs) are promising optoelectronic materials due to their unique properties, such as tunable band gap and strong absorption, which are of immense interest for application in photodetectors and solar cells. However, the tunable band gap of PbS CQDs would only cover visible short-wave infrared; the ability to detect longer wavelengths, such as mid- and long-wave infrared, is limited because they are restricted by the band gap of the bulk material. In this paper, a novel photodetector based on the synergistic effect of PbS CQDs and bismuth telluride (Bi₂Te₃) was developed for the detection of a mid-wave infrared band at room temperature. The device demonstrated good performance in the visible-near infrared band (i.e., between 660 and 850 nm) with detectivity of 1.6 × 10¹⁰ Jones at room temperature. It also exhibited photoelectric response in the mid-wave infrared band (i.e., between 4.6 and 5.1 μm). The facile fabrication process and excellent performance (with a response of up to 5.1 μm) of the hybrid Bi₂Te₃/PbS CQDS photodetector are highly attractive for many important applications that require high sensitivity and broadband light detection.

Room-Temperature Infrared Photodetectors with Zero-Dimensional and New Two-Dimensional Materials

Infrared photodetectors have received much attention for several decades due to their broad applications in the military, science, and daily life. However, for achieving an ideal signal-to-noise ratio and a very fast response, cooling is necessary in those devices, which makes them bulky and costly. Thus, room-temperature infrared photodetectors have emerged as a hot research direction. Novel low-dimensional materials with their easy fabrication and excellent photoelectronic properties provide a possible solution for room-temperature infrared photodetectors. This review aims to summarize the preparation methods and characterization of several low-dimensional materials (PbS, PbSe and HgTe, new two-dimensional materials) with great concern and the room-temperature infrared photodetectors based on them.

Promoted Mid-Infrared Photodetection of PbSe Film by Iodine Sensitization Based on Chemical Bath Deposition

In recent years, lead selenide (PbSe) has gained considerable attention for its potential applications in optoelectronic devices. However, there are still some challenges in realizing mid-infrared detection applications with single PbSe film at room temperature. In this paper, we use a chemical bath deposition method to deposit PbSe thin films by varying deposition time. The effects of the deposition time on the structure, morphology, and optical absorption of the deposited PbSe films were investigated by x-ray diffraction, scanning electron microscopy, and infrared spectrometer. In addition, in order to activate the mid-infrared detection capability of PbSe, we explored its application in infrared photodetection by improving its crystalline quality and photoconductivity and reducing tge noise and high dark current of PbSe thin films through subsequent iodine treatment. The iodine sensitization PbSe film showed superior photoelectric properties compared to the untreated sample, which exhibited the maximum of responsiveness, which is 30.27 A/W at 808 nm, and activated its detection ability in the mid-infrared (5000 nm) by introducing PbI₂, increasing the barrier height of the crystallite boundary and carrier lifetimes. This facile synthesis strategy and the sensitization treatment process provide a potential experimental scheme for the simple, rapid, low-cost, and efficient fabrication of large-area infrared PbSe devices.

Study on SO2 and Cl2 sensor application of 2D PbSe based on first principles calculations

In this paper, we use 2D PbSe to design a gas sensor to monitor the presence of SO2 and Cl2. We use first principles to verify the feasibility of this material, such as atomic structure, band gap, differential charge density and Bader charge. The results show that 2D PbSe can distinctly adsorb SO2 and Cl2. Furthermore, the adsorption of SO2 and Cl2 will affect the electronic structure of 2D PbSe, and some electrons in the PbSe are transferred to gas atoms. The band gap of the system after adsorption is smaller than that of the PbSe before adsorption. The band gap of single layer PbSe decreases by 41.92% after SO2 adsorption and 60.61% after Cl2 adsorption. The band gap of multi-layer PbSe decreases by 72.97% after SO2 adsorption and 43.24% after Cl2 adsorption. This shows that single layer PbSe is more sensitive to Cl2 and multi-layer PbSe is more sensitive to SO2. It provides a potential possibility for designing gas sensors for SO2 and Cl2 based on 2D PbSe.

Tunable Performance of Quantum Dot-MoS2 Hybrid Photodetectors via Interface Engineering

Heterostructures of quantum dots (QDs) and two-dimensional (2D) materials show promising potential for photodetection applications owing to their combination of high optical absorption and good in-plane carrier mobility. In this work, the performance of QD-2D photodetectors is tuned by band engineering. Devices are fabricated by coating MoS₂ nanosheets with InP QDs, type-I core-shell InP/ZnS QDs, and type-II core-shell InP/CdS QDs. Comparative spectroscopic and photoelectric studies of different hybrids show that the energy band alignment and shell thickness can influence the efficiency of charge transfer (CT), energy transfer (ET), and defect-related processes between QDs and MoS₂. Benefiting from efficient CT between the QDs and MoS₂, a significant enhancement of responsivity and detectivity is observed in thick-shell InP/CdS QD-MoS₂ devices. Our results demonstrate the feasibility of using core-shell QDs for regulating the ET and CT efficiency in heterostructures and highlight the importance of interface band design in QD-2D and other low-dimensional photodetectors.

Rapid In Situ Ligand-Exchange Process Used to Prepare 3D PbSe Nanocrystal Superlattice Infrared Photodetectors

Colloidal semiconductor nanocrystals are important building blocks for low-cost, solution-processed electronic devices with tunable functionalities. Considerable progress is made in improving charge transport through nanocrystal films by exchanging long insulating ligands with shorter passivating ligands. To take full advantage of this strategy, it is equally important to fabricate close-packed structures that reduce the average interparticle spacing. Yet it remains a challenge to retain long-range, close-packed order after ligand exchange. Here, a novel one-step in situ ligand-exchange method is demonstrated that enables rapid (5 min) ligand exchange of nanocrystal films, which are more than 50 layers thick. Using this simple and efficient method, it is shown that the face-centered cubic ordering of 500 nm thick PbSe nanocrystal films is retained after ligand exchange from oleic acid to benzoic acid. Moreover, it is demonstrated that PbSe nanocrystal photodetectors with a well-ordered structure have superior optoelectronic properties compared to disordered films; ordered films have a 16× higher responsivity of ≈0.25 A W^-1 at 1 V and a 2× faster response time. As far as it is known, this is the first report to realize a rapid one-step ligand exchange through a thick superlattice film with retention of long-range order.

MoS2 Based Photodetectors: A Review

Photodetectors based on transition metal dichalcogenides (TMDs) have been widely reported in the literature and molybdenum disulfide (MoS2) has been the most extensively explored for photodetection applications. The properties of MoS2, such as direct band gap transition in low dimensional structures, strong light-matter interaction and good carrier mobility, combined with the possibility of fabricating thin MoS2 films, have attracted interest for this material in the field of optoelectronics. In this work, MoS2-based photodetectors are reviewed in terms of their main performance metrics, namely responsivity, detectivity, response time and dark current. Although neat MoS2-based detectors already show remarkable characteristics in the visible spectral range, MoS2 can be advantageously coupled with other materials to further improve the detector performance Nanoparticles (NPs) and quantum dots (QDs) have been exploited in combination with MoS2 to boost the response of the devices in the near ultraviolet (NUV) and infrared (IR) spectral range. Moreover, heterostructures with different materials (e.g., other TMDs, Graphene) can speed up the response of the photodetectors through the creation of built-in electric fields and the faster transport of charge carriers. Finally, in order to enhance the stability of the devices, perovskites have been exploited both as passivation layers and as electron reservoirs.